It is known that reactions of the above type are catalyzed by a Group VIII metal such as cobalt. For example, EP-A-143911 discloses the preparation of succinic diesters starting from an acrylic ester and using a cobalt carbonyl complex as catalyst. This known process suffers from the disadvantage of requiring rather severe reaction conditions, such as a carbon monoxide pressure of 120-130 bar. A further process using a cobalt catalyst is described in JP-A-83/72539.
In EP-A-274795, a process is described for the carbonylation of olefinically unsaturated compounds with a palladium catalyst. The exemplified catalyst systems comprise a source of palladium, a triarylphosphine, a strong acid and a stabilizer, such as phosphine oxides and sulfides, or tertiary acids. According to its specification, the olefinic substrate may be substituted with a broad class of functional groups, including acid, ester, acid amide and acid nitrile groups, but no experimental data on the achievable conversions and selectivities are given.
It has now been found that alkanedioc acid derivatives can be prepared under mild conditions by carbonylation, if use is made of a specific catalyst system. Using this catalyst system, good conversions and excellent selectivities to the desired products are obtained.